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About this Project

FST was lead designer for the Turner Center Bridge over the Androscoggin River, a replacement for the steel bridge that connected the Maine towns of Turner and Greene.

The design-build project for the MaineDOT teams FST with contractor Reed & Reed Construction (R&R) to replace the 400-foot-long, 90-year-old two-span steel truss bridge. FST’s design uses two-span, horizontally curved haunched steel girders with a total length of 480 feet. The haunched girder design, coupled with the vertical curve on the bridge, minimized the extent of the approach work and reduced project costs while satisfying the clearance above the design flood level. The substructure was designed for ice loading due to the ice flows that are common in the river at this location. The foundations consist of spread footings on tremie seals that extend to bedrock and require cofferdams up to 35 feet in depth.

An additional challenge was the need to keep traffic flowing throughout construction; the closest crossing is 20 miles away, so a detour was not possible.To meet schedule, FST prepared plans in stages and obtained approval for the early release of individual bridge components for construction. This approach, coupled with a fast track design, allowed R&R to being work on critical path bridge components which enabled the work to be sequenced around the in-water work windows.

The new bridge ties into the approach roadway near the existing abutments, providing the necessary river waterway opening. It was also essential that the abutment and approach design satisfy the environmental commitments regarding minimal disturbance of the protected riparian areas in the river. The FST design minimized right-of-way impacts and grade changes at the approaches while satisfying abutter concerns regarding drainage issues.

3D modeling was essential to the design process. FST modelers developed nine bridge and approach alignment alternatives, which the team then used 3D modeling software to evaluate for cost, clearance, constructability, and environmental impact. In this way, the FST/R&R team efficiently evaluated and selected the preferred alternative. The chosen alternative was further developed and detailed into final construction plans using this 3D modeling software. In this manner, FST met and exceeded design objectives for complex road and bridge geometry (e.g., superelevated horiztonal curves, multiple successive vertical curves, intersection grading), as well as surface and subsurface drainage designs. Modeling also prevented conflicts with existing and relocated utilities and an underwater environmental monitoring station.

The projectbecame fully operational in December 2014.

More Information

Owner: Maine Department of Transportation

Location: Turner and Greene, Maine

Highlights: The project won the American Council of Engineering Companies of New Hampshire (ACEC-NH) Engineering Excellence Award for Structural Systems in March 2015.